chore: add test verifying PnP works

.github/workflows/nodejs.yml

@@ -74,6 +74,8 @@ jobs:
         run: yarn test-types
       - name: verify TypeScript@3.8 compatibility
         run: yarn verify-old-ts
+      - name: verify Yarn PnP compatibility
+        run: yarn verify-pnp
       - name: run eslint
         run: yarn lint
       - name: run prettier

package.json

@@ -107,6 +107,7 @@
     "test-leak": "yarn jest -i --detectLeaks jest-mock jest-diff jest-repl pretty-format",
     "test": "yarn lint && yarn jest",
     "verify-old-ts": "node ./scripts/verifyOldTs.js",
+    "verify-pnp": "node ./scripts/verifyPnP.js",
     "watch": "yarn build:js && node ./scripts/watch.js",
     "watch:ts": "yarn build:ts --watch"
   },

scripts/verifyPnP.js

@@ -0,0 +1,65 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+'use strict';
+
+const fs = require('fs');
+const path = require('path');
+const chalk = require('chalk');
+const dedent = require('dedent');
+const execa = require('execa');
+const rimraf = require('rimraf');
+const tempy = require('tempy');
+
+const rootDirectory = path.resolve(__dirname, '..');
+
+const cwd = tempy.directory();
+
+try {
+  fs.writeFileSync(
+    path.join(cwd, '.yarnrc.yml'),
+    dedent`
+      enableGlobalCache: true
+
+      yarnPath: ${require.resolve('../.yarn/releases/yarn-2.4.2.cjs')}
+    `,
+  );
+  fs.writeFileSync(
+    path.join(cwd, 'package.json'),
+    JSON.stringify(
+      {
+        dependencies: {
+          jest: `*`,
+        },
+        name: 'test-pnp',
+      },
+      null,
+      2,
+    ),
+  );
+  fs.writeFileSync(
+    path.join(cwd, 'test.js'),
+    dedent`
+     /*
+      * @jest-environment jsdom
+      */
+
+     test('dummy', () => {
+       expect(window).toBeDefined();
+     });
+    `,
+  );
+  execa.sync('yarn', ['link', '--private', '--all', rootDirectory], {
+    cwd,
+    stdio: 'inherit',
+  });
+  execa.sync('yarn', ['jest'], {cwd, stdio: 'inherit'});
+
+  console.log(chalk.inverse.green(` Successfully ran Jest with PnP linker `));
+} finally {
+  rimraf.sync(cwd);
+}